Since a bearing roller chain is adapted to high speed and high load in a case of the transmission of power, it has been widely used as a high speed transmission chain and a conveyor chain. And in the use of the bearing roller chain in an atmosphere of dust, an atmosphere of water splashing or the like, a seal mechanism is provided between an inner link plate and a bearing roller in a chain to prevent invasion or entry of foreign substances between the bearing roller and a bush which rotatably supports the bearing roller and to prevent the scattering of grease or oil sealed between a bearing roller and the bush. Various seal mechanisms have been proposed.
FIG. 5 is an enlarged cross-sectional view of a conventional bearing roller chain. The bearing roller chain 21 provides inward flanges 22a on both sides of a hollow roller 22. A number of anti-friction rollers 24 are disposed between the hollow roller 22 and a bush 23. A thrust ring 27 composed of a low frictional, wear-resistant synthetic resin and an oleo-sintered metal as a seal mechanism is provided between the hollow roller 22 and an inner link plate 25. Further, a lubricating-oil-filled space 28 is provided inside the thrust ring 27. It is noted that the reference numeral 26 denotes an outer link plate and the reference numeral 29 denotes a connecting pin.
In the above-mentioned conventional bearing roller chain, a seal mechanism 22 is a one-layered structure composed of a thrust ring 27 provided between a roller 22 and an inner link plate 25. The seal performance is not sufficient and when the thrust ring 27 has a low close contact with the roller 22 or the inner link plate 25, lubricating oil can leak out of any space or gap between an end surface of the hollow roller 22 and the thrust ring 27. Further, there is a problem that foreign substances such as dust, water or the like may enter through the gap to mix into the lubricating oil so that wear of the roller 22, the bush 23, the roller 24 and the like is promoted, resulting in failure of the roller's rotation generated by the wear, and the life of the chain is shortened. In this case, there is a problem that when close adherence properties are increased so as to avoid generating a gap between the thrust ring 27 and the roller 22 or the inner link plate 25, traveling resistance of the chain is increased and power required to drive the conveyor is increased.